Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$224.71	9.268%	$245.5361	$245.54	$245.55	$245.50
Purchase #2	$100.86	8.784%	$109.7195	$109.72	$109.70	$109.70
Purchase #3	$12.41	3.311%	$12.8209	$12.82	$12.80	$12.80
Purchase #4	$51.43	11.290%	$57.2364	$57.24	$57.25	$57.20
Purchase #5	$85.61	11.584%	$95.5271	$95.53	$95.55	$95.50
Purchase #6	$104.45	3.647%	$108.2593	$108.26	$108.25	$108.30
Purchase #7	$121.95	4.727%	$127.7146	$127.71	$127.70	$127.70
7 purchase totals =	$701.42		$756.8139	$756.82	$756.80	$756.70